Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$107.67	3.799%	$111.7604	$111.76	$111.75	$111.80
Purchase #2	$135.82	5.222%	$142.9125	$142.91	$142.90	$142.90
Purchase #3	$17.88	4.470%	$18.6792	$18.68	$18.70	$18.70
Purchase #4	$241.41	11.414%	$268.9645	$268.96	$268.95	$269.00
Purchase #5	$155.99	13.416%	$176.9176	$176.92	$176.90	$176.90
Purchase #6	$84.43	8.486%	$91.5947	$91.59	$91.60	$91.60
Purchase #7	$179.71	6.251%	$190.9437	$190.94	$190.95	$190.90
7 purchase totals =	$922.91		$1,001.7726	$1,001.76	$1,001.75	$1,001.80